• Steven Rostedt's avatar
    ftrace: enable filtering only when a function is filtered on · e68746a2
    Steven Rostedt authored
    Impact: fix to prevent empty set_ftrace_filter and no ftrace output
    
    The function filter is used to only trace a given set of functions.
    The filter is enabled when a function name is echoed into the
    set_ftrace_filter file. But if the name has a typo and the function
    is not found, the filter is enabled, but no function is listed.
    
    This makes a confusing situation where set_ftrace_filter is empty
    but no functions ever get enabled for tracing.
    
    For example:
    
     # cat /debug/tracing/set_ftrace_filter
    
      #### all functions enabled ####
    
     # echo bad_name > set_ftrace_filter
     # cat /debug/tracing/set_ftrace_filter
    
     # echo function > current_tracer
     # cat trace
    
      # tracer: nop
      #
      #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
      #              | |       |          |         |
    
    This patch changes that to only enable filtering if a function
    is set to be filtered on. Now, the filter is not enabled if
    a bad name is echoed into set_ftrace_filter.
    Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
    e68746a2
ftrace.c 47.2 KB